1. Field of the Invention
This invention relates to a compression processing method of real number data in a processing system and apparatus therefor. More particularly, the present invention relates to a real number data compression processing method and apparatus capable of reducing a memory capacity necessary for processing and preserving real number data.
2. Description of the Related Art
A processing system for executing various processings by the use of real number data has been used in many fields.
The problem with such a processing system is the extent to which the significant digits of the real number data to be handled should be guaranteed, and 15 digits and 64 bits are ordinarily guaranteed at present.
This results from the fact that the digits of the processed data are generally 15 digits when various processings are executed in a memory as a memory means used in the processing system.
When the data after processing are stored and preserved in a suitable medium such as a tape or a disc, however, the data need not always be guaranteed accurate throughout the fifteen digits and in some cases, it will be sufficient if accuracy is guaranteed for ten digits.
Therefore, when the data are preserved, compression processing, which rounds down or cuts off the data to a suitable digit and compresses the real number data, has been carried out.
On the other hand, the data are different from system to system in accordance with the field in which the processing system is employed, and quite naturally, the significant digits of the data are different in accordance with the field in which they are dealt with.
In a processing system associated with daily accounting, for example, the order of the real number data handled is 10.sup.0 or more but in the field of design requiring ultra-high accuracy such as in an LSI design, the order of the real number data is from to 10.sup.-9 to 10.sup.0.
Furthermore, the real number data in processing in the field of architectural design are in the order of 10.sup.-3 to 10.sup.2.
In other words, it is very important in such a processing system to which position of the order the significant digit should be set because the real number data to be dealt with by the system vary even though a hardware used remains the same. Therefore, softwares have conventionally been so designed as to recognize the data value in the order of to 10.sup.-9 to 10.sup.+2, for example, as the significant digit so that processing can be executed in various fields by the use of the same processing system.
In accordance with the conventional system, however, the significant digit of the real number data has been equally rounded down to a predetermined digit. For example, the real number data used for all the processings are limited to 10 digits from the most significant digit and the data of the other digits are all cut off.
As described above, the significant digit of the real number data used in the processing system varies with the field in which the system is used. Even though no problem is encountered when the real number data up to the tenth digit from the most significant digit are used for the real number data in processing the architectural design, such a method is not sufficient and an accurate design cannot be made in the case of an LSI design when the fifth to fifteenth digits from the most significant digit are used as the significant digits.
When a drawing such as a map is depicted and displayed by the use of a CAD system, the real number data in the order of at most 6 digits are used; hence, it is not necessary to secure ten digits as the significant digits and this is a so-called "over-specification" state.
One of the methods of solving these problems is to change the memory capacity in accordance with the significant digits of the real number data required in the respective fields, but such a method is not an economical processing system because the memory capacity becomes great.